Lower limb assistive devices, such as lower limb prostheses, orthoses, or exoskeletons, may be used by individuals who need the help of such a device. A prosthesis, for instance, may be used by a person who has lost a lower limb by amputation. An orthosis may be used by a person whose lower limb has been weakened by injury or disease, such as a stroke.
A lower limb assistive device may be powered by an external source, such as a battery and electric motor. Powered lower limb assistive devices assist a user's movement. For instance, when a user of a lower limb assistive device is climbing stairs, the device must provide power when the foot of the device is placed on a stair and the user shifts her weight onto the device, so as to propel the user up the stair. As another example, a user who wishes to move from a sitting to a standing position shifts her weight onto her lower limb(s) and lower limb assistive device. The assistive device must provide power to assist the user in transitioning from a sitting posture to a standing posture. Powered lower limb assistive devices known in the art provide users with limited control over the moment when power is applied and the rate at which power is applied. Amputees without adequate powered control of a lower limb assistive device ultimately end up using their good limb, rather than the assistive device, to bear weight in these and other tasks.